This project is fundamentally concerned with investigations designed to elucidate: (1) functional neuronal networks of the vertebrate retina and their role in the visual process; (2) the specific relationship between intracellular (neural, glial, and pigment epithelial) and extracellular potentials so that the electroretinogram (ERG) and other retinal potential might be unequivocally interpreted; and (3) the interactions between neurons and glia, including cases in which retinal excitability is altered (e.g., spreading depression) or which generate significant field-potentials. Electrophysiological techniques for recording intra- and extracellular potentials will be combined with methods for computing current source densities and measuring ionic fluxes in order to explore stimulus-dependent mechanisms of retinal information processing. The retina of the mudpuppy will be used because of its comparatively larger cells which offer a unique opportunity to quantitatively relate the activity of preganglionic neurons to the impulse discharge patterns of the three classes of ganglion cells found in this animal. It is expected that these observations will aid in clarifying remaining questions related to the origin of ERG components and thereby add further to the interpretative utility of the ERG in clinical optholmological diagnoses. This research will also contribute to a more conprehensive picture of retinal organization and to an understanding of ionic interactions between neurons and glial cells.